Clinical Chemistry
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Clinical Chemistry 37: 1185-1190, 1991;
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Clinical Chemistry, Vol 37, 1185-1190, Copyright © 1991 by American Association for Clinical Chemistry

Micro-quantification of cyclosporine and its metabolites and determination of their spectral absorptivities [published erratum appears in Clin Chem 1992 Feb;38(2):323]

I Fu and LD Bowers
Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis 55455.

We report a micromethod for the analysis of cyclosporine (CsA), based on quantification of its constituent amino acids. The amino acids were released by gas-phase hydrolysis, derivatized with fluorenylmethyl chloroformate, and separated and analyzed in a reversed-phase HPLC system. The imprecision (CV) of the amino acid analysis was less than 4%, and several determinations of the amount of standard CsA were within 1% of the weighed material. The detection limits (signal-to- noise ratio = 2) were 500 fmol for ultraviolet detection and 100 fmol for fluorescence detection. We also used this method to determine the ultraviolet absorptivities of CsA and five metabolites at 210, 214, and 230 nm. The molar absorptivity of most metabolites was about 10% higher than that of CsA, although the metabolite that was oxidized to a carboxyl group on the terminal carbon of N-methyl-butenyl-methyl- threonine (AM1A) had a molar absorptivity about 40% higher than that of CsA.




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Copyright © 1991 by the American Association for Clinical Chemistry.